MAX639 Datasheet, PDF (1/12 Pages) Maxim Integrated Products – 5V/3.3V/3V/Adjustable, High-Efficiency, Low IQ, Step-Down DC-DC Converters

19-4505; Rev 3; 8/97
5V/3.3V/3V/Adjustable, ^{INFOERVMALAUTAIOTNIOINNCKLITUDED} High-Efficiency,
Low I_Q, Step-Down DC-DC Converters
_______________General Description
The MAX639/MAX640/MAX653 step-down switching
regulators provide high efficiency over a wide range of
load currents, delivering up to 225mA. A current-limiting
pulse-frequency-modulated (PFM) control scheme gives
the devices the benefits of pulse-width-modulated
(PWM) converters (high efficiency at heavy loads), while
using only 10µA of supply current (vs. 2mA to 10mA for
PWM converters). The result is high efficiency over a
wide range of loads.
The MAX639/MAX640/MAX653 input range is 4V to
11.5V, and the devices provide lower preset output volt-
ages of 5V, 3.3V, and 3V, respectively. Or, the output
can be user-adjusted to any voltage from 1.3V to the
input voltage.
The MAX639/MAX640/MAX653 have an internal 1A power
MOSFET switch, making them ideal for minimum-compo-
nent, low- and medium-power applications. For increased
output drive capability, use the MAX649/MAX651/MAX652
step-down controllers, which drive an external P-channel
FET to deliver up to 5W.
________________________Applications
9V Battery to 5V, 3.3V, or 3V Conversion
High-Efficiency Linear Regulator Replacement
Portable Instruments and Handy-Terminals
5V-to-3.3V Converters
____________________________Features
o High Efficiency for a Wide Range of Load Currents
o 10µA Quiescent Current
o Output Currents Up to 225mA
o Preset or Adjustable Output Voltage:
5.0V (MAX639)
3.3V (MAX640)
3.0V (MAX653)
o Low-Battery Detection Comparator
o Current-Limiting PFM Control Scheme
______________Ordering Information
PART
MAX639CPA
MAX639CSA
MAX639C/D
MAX639EPA
MAX639ESA
MAX639MJA
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
8 CERDIP
Ordering Information continued on last page.
* Contact factory for dice specifications.
__________Typical Operating Circuit __________________Pin Configuration
INPUT
5.5V TO 11.5V
V+
LX
OUTPUT
5V
225mA
ON/OFF
LOW-BATTERY
DETECTOR
INPUT
MAX639
SHDN
VOUT
LBI
LBO
VFB
GND
LOW-BATTERY
DETECTOR
OUTPUT
TOP VIEW
VOUT ₁
LBO 2
LBI 3
GND ₄
MAX639
MAX640
MAX653
DIP/SO
8 SHDN
7 VFB
6 V+
5 LX
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